title: Value of diffusion-weighted magnetic resonance imaging for prediction and early assessment of response to neoadjuvant radiochemotherapy in rectal cancer: preliminary results.
abstract: OBJECTIVE
  To evaluate diffusion-weighted magnetic resonance imaging (DWI) for response prediction before and response assessment during and early after preoperative radiochemotherapy (RCT) for locally advanced rectal cancer (LARC).
  
  
  METHODS
  Twenty patients receiving RCT for LARC underwent MRI including DWI before RCT, after 10-15 fractions and 1 to 2 weeks before surgery. Tumor volume and apparent diffusion coefficient (ADC; b-values: 0-1000 s/mm(2)) were determined at all time points. Pretreatment tumor ADC and volume, tumor ADC change (∆ADC), and volume change (∆V) between pretreatment and follow-up examinations were compared with histopathologic findings after total mesorectal excision (pathologic complete response [pCR] vs. no pCR, ypT0-2 vs. ypT3-4, T-downstaging or not). The discriminatory capability of pretreatment tumor ADC and volume, ∆ADC, and ∆V for the detection of pCR was compared with receiver operating characteristics analysis.
  
  
  RESULTS
  Pretreatment ADC was significantly lower in patients with pCR compared with patients without (in mm(2)/s: 0.94 ± 0.12 × 10(-3) vs. 1.19 ± 0.22 × 10(-3), p = 0.003), yielding a sensitivity of 100% and specificity of 86% for detection of pCR. The volume reduction during and after RCT was significantly higher in patients with pCR compared with patients without (in %: ΔV(during): -62 ± 16 vs. -33 ± 16, respectively, p = 0.015; and ΔV(post): -86 ± 12 vs. -60 ± 21, p = 0.012), yielding a sensitivity of 83% and specificity of 71% for the ΔV(during) and, respectively, 83% and 86% for the ΔV(post). The ∆ADC during (ΔADC(during)) and after RCT (ΔADC(post)) showed a significantly higher value in patients with pCR compared with patients without (in %: ΔADC(during): 72 ± 14 vs. 16 ± 12, p = 0.0006; and ΔADC(post): 88 ± 35 vs. 26 ± 19, p = 0.0011), yielding a sensitivity and specificity of 100% for the ΔADC(during) and, respectively, 100% and 93% for the ΔADC(post).
  
  
  CONCLUSIONS
  These initial findings indicate that DWI, using pretreatment ADC, ΔADC(during), and ΔADC(post) may be useful for prediction and early assessment of pathologic response to preoperative RCT of LARC, with higher accuracy than volumetric measurements.
authors.affiliation: Department of Radiation Oncology, UZ Gasthuisberg, Leuven, Belgium. maarten.lambrecht@uzleuven.be
authors.forename: Maarten
authors.initials: M
authors.lastname: Lambrecht
authors.forename: Vincent
authors.initials: V
authors.lastname: Vandecaveye
authors.forename: Frederik
authors.initials: F
authors.lastname: De Keyzer
authors.forename: Sarah
authors.initials: S
authors.lastname: Roels
authors.forename: Freddy
authors.initials: F
authors.lastname: Penninckx
authors.forename: Eric
authors.initials: E
authors.lastname: Van Cutsem
authors.forename: Claus
authors.initials: C
authors.lastname: Filip
authors.forename: Karin
authors.initials: K
authors.lastname: Haustermans
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage; D059186:Chemoradiotherapy, Adjuvant / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D019583:Dose Fractionation, Radiation; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009944:Organoplatinum Compounds / Q000008:administration & dosage; D000077150:Oxaliplatin; D057234:Preoperative Period; D012372:ROC Curve; D012004:Rectal Neoplasms / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D012007:Rectum / Q000601:surgery; D012074:Remission Induction / Q000379:methods; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D047368:Tumor Burden / Q000528:radiation effects
chemical_list: D000964:Antimetabolites, Antineoplastic; D009944:Organoplatinum Compounds; D000077150:Oxaliplatin; D005472:Fluorouracil